Connection using zebra strip

ABSTRACT

The present invention concerns a housing for a price-marking device comprising a thin LCD (30) and a printed circuit board (20) with control electronics and power supply, e.g. a solar cell. The thin LCD (30) is connected to the underlying printed circuit board (30) by a connection device containing conductive rubber areas. Such a device is referred to as a zebra contact strip, the zebra contact strip (15) being arranged between the LCD (30) and the printed circuit board by means of longitudinal parallel enclosing edges (12a, 12b) on the extruded housing (10) preferably made of plastic material and being compressed in a direction across the conducting rubber areas by the action of the longitudinal parallel enclosing edges (12a, 12b) which upon extrudation have been given an inward directed biasing force.

FIELD OF INVENTION

The present invention relates to connection by means of a so called"zebra strip" or zebra contact, and more exactly by means of an extrudedplastic housing to achieve the pressure necessary to connect a displayin form of a LCD (Liquid Crystal Device) to a printed circuit board(PCB) by means of a zebra contact.

BACK OF THE INVENTION

For displaying of e.g. price information and other additionalinformation of a merchandise in a shop, normally a price-marking labelpositioned at the forward edge of the shelf carryinq the merchandise isutilized. According to the state of the art today there is a wish toreplace these price labels by electronic units being controlled by asuitable central computer. By this method a great part of the tediouslabor for price marking will be avoided at the same time as a guaranteeis obtained that the marking of the edge of the shelf will be displayingthe price known by the computer and which then controls the registrationdevice at the exit cash register. A demand for such an electronic devicefor the marking of shelves is that it among other things should be thinnot to occupy unnecessary space and should present a correspondingfunction as of the previous price-marking label, being most often a thinpiece of paper

To accomplish connection between a printer circuit board and a displayin the form of a LCD (Liquid Crystal Display) for such a display for theedge of a shelf one way is to utilize conductive rubber. Such aconductive rubber device is normalIy referred to as a so called "zebrastrip" or zebra contact, why this device. To obtain a proper connectionit is required that the conductive rubber should be compressed by about15%. This compression is necessary to decrease the contact resistance.For this traditionally metal housings having wings which are bent uponassembly have been utilized or screwed joint reinforcements between theprinted circuit board and the plastic or metal housings have been used.

All these methods are space consuming and are not suitable for thinproducts. To connect thin products a method was developed where a LCDand circuit board were joined by means of a flexible printed board andan electrically conducting fusible glue, so called "heat seal". Thismethod however is very prolix and thereby expensive, especially when theLCD has contacts along two or more of its sides.

A SHORT DESCRIPTION OF THE INVENTION

The present invention offers a low-price and practical solution of theabove mentioned problem by supplying an extruded housing of preferablyPVC plastics for a price-marking device having a display window in formof a LCD, whereby the desired pressure for the compression of theconductive rubber in a zebra contact is achieved by means of a biasingforce of the outer forward edge or edges of the plastic structuralprofile.

An additional object of the present invention is that the outer forwardenclosing edge of the housing then centrally over the centrum of thezebra contact, which is making the connection to the LCD), is acting asa lever putting pressure to the glass constituting the front side of theLCD.

Another additional object of the present invention is to furtherconserve the created pressure by means of a plate member, preferably outof steel or any other rigid material, which member is insert intoundercut slot along the edge of the longitudinal side of the housing tothe housing to thereby prevent misrun of the housing plastics and adecreasing pressure against the front side of the LCD.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in form of a preferred embodiment bymeans of the attached drawings which show:

FIG. 1 a price-marking device comprising a display of LCD type and asolar cell for energy supply and having an area for a product label,

FIG. 2 an exemplifying portion of a printed circuit board for connectiona display of LCD type, shown in FIG. 1,

FIG. 3 a partly intersected illustration of a zebra contact,

FIG. 4 an intersection of the right portion of the price-marking deviceof FIG. 1 formed as an extruded plastic housing according to the presentinvention, and

FIG. 5 an intersection of the left portion of the price-marking deviceof FIG. 1 formed as an extruded plastic housing according to the presentinvention.

A PREFERRED EMBODIMENT

FIG. 1 demonstrates in a preferred embodiment a price-marking device 1intended to be attached to an edge of a shelf. The device 1 iscomprising a display which constitutes a LCD 30 which by 7-segmentcharacter technique shows e.g. the price of an article, a comparisonprice and an ordinary price if the article temporarily being pricereduced. The field for the comparison price is having a yellowbackground in the embodiment. Additionally the device comprises a solarcell 3 for energy supply of the device 1 and a label field 4 forinsertion of a paper having a preprinted article information whichnormally will be delivered with a large packing of a merchandise. Thedevice further consists of a printed circuit board having a number ofintegrated circuits and other electronic components such as e.g. an IRreceiver for transmission of price information to the price-markingdevice from a central computer his printed circuit board additionallyprovides the LCD 30 with control voltages. The total device is containedin a thin extruded structural profile or a housing 10 preferably out ofa plastic material. In FIG. 2 is demonstrated an enlarged portion of theprinted circuit pattern of the printed circuit board 20, which portionshown for the LCD 30 includes a multitude of connector terminals 21 and22, respectively, whereby the LCD provides corresponding terminal fields(not shown). As shown by FIG. 2 a large number of contact points areneeded, which then must be made having a relatively small graduation tofacilitate a compact size of the printed circuit board and consequentlyof the price-marking device, whereby principally the width of the LCDwill mainly decide the size of the device. In the embodiment thisconnection between the printed circuit board and the LCD is made bymeans of an arrangement of conductive rubber in form of two zebracontact strips 15 (FIG. 4), one at the upper edge of the printed circuitboard and the LCD 30 and one at the lower edge of the printed circuitboard and the LCD 30.

The principle of such a zebra contact strip is shown in FIG. 3. The darkareas 16 consist of conducting rubber while the rest of the stripconstitutes nonconducting material 17. To accomplish contact between theprinted circuit board 20 and the LCD 30 such a zebra contact strip 15 ispositioned over the terminal fields 21 and 22, respectively, and theLCD, on the rear side having corresponding contacts, is then positionedon top of- the zebra contacts by the pitch of the pattern is alwaysensured that at least a part, preferably all, of the conducting rubberis landing against the terminal fields 21 and 22, respectively in asimilar way due to the pitch of the pattern it is not possible that theconducting rubber may land over two contact and short-circuit these. Toobtain an acceptable electrical transmission line between the printedcircuit board and the LCD it is desirable that the zebra contact iscompressed by at least about 15% by compressing the LCD and the orientedcircuit board against each other in a suitable way. This contactpressure is achieved by a special extruded structural profile or ahousing 10 preferably out of a PVC plastic material.

Finally FIG. 4 is showing an intersection of the price-marking device 1,shown in Fig. 1, at its left side comprising the solar cell 4, whichpreferably presents a thickness approximately corresponding to the totalLCD 30 including its reflector 31, rear glass 32 and front glass 33 aswell as polarization filter 34. The solar cell rests in a suitable wayagainst the printed circuit board e.g. by means of a resilient materialbetween the printed circuit board and the solar cell. The portionconstituting the base for the label 4 preferably is made out of aplastic plate having the same thickness as the solar cell. Thus, inanother embodiment it is simple e.g. To have the solar cell 3 and thelabel 4 to change place.

The housing 10 presents a somewhat biased frame edge 12a and 12b,respectively, which above all will exert the desired pressure upon theLCD to achieve a suitable compression of the zebra contact or the zebracontacts. The frame edges 12a and 12b, respectively, additionallypresent edge slots 13a and 13b, respectively, for reception of a label4. The housing 1 of the embodiment further at its upper and lowerlongitudinal edges presents an undercut slot 14 which is intended forreceiving a strip of metal or plastic to further stiffen the housingwhen the printed circuit board 20, the LCD 30 and the solar cell 3 areassembled within the housing 10. The strip may be given a U form havinga distance between the shanks corresponding to the shorter sides of theprice-marking device 1. The length of the shanks then preferably areequal to half the length of the device 1, whereby such a U form will beinserted in the upper slot 14a and the lower slot 14b from eachdirection at the shorter sides. In another embodiment the shanksconstitute two lying L forms which in a corresponding way are insertedeach from its different side. However, making the housing out of asuitable material by extrudating, it has unexpectedly be found topossess a sufficient resilient force in the frame edges 12a and 12b, whyas such the additional strips in the undercut slots 14a and 14b onlyconstitute a further locking at the same time as the strips anyhow areoffering an additional protection of the edges of the price-markingdevice 1.

By means of the housing in accordance with the present invention whichfacilitates simple connection by zebra contacts, a very compact deviceregarding thickness is obtained at the same time as it is very cheap toproduce and simple to assemble and is presenting the desiredcharacteristics.

I claim:
 1. A method in connection to a price-marking device (1)comprising a thin LCD (30) and a printed circuit board (20) with controlelectronics and power supply, e.g. a solar cell, for the connection ofsaid thin LCD (30) to said printed circuit board (20) by means of aconnection device of conductive rubber in form of a so called zebracontact strip (15), characterized inthat said zebra contact strip (15)in a direction across the conducting rubber areas is compressed betweensaid thin LCD (30) and said printed circuit board (20) by means of anextruded housing (10), preferably out of plastic material, the outerforward enclosing edges (12a, 12b) of which are biased upon production,that at least the longitudinal parallel enclosing edges (12a, 12b) ofsaid housing in design and material are biased such that inner surfacesof said longitudinal parallel enclosing edges are centered over thecenter of the zebra contact (15) along the corresponding edges of saidthin LCD (30) and said printed circuit board (20) comprising terminalfields (21, 22) for signal transmission between said thin LCD and theprinted circuit board is acting as a lever exerting pressure against aglass (33) constituting the front side of said thin LCD, whereby acompression of at least 15% of the conducting rubber of said zebracontact (15) is accomplished.
 2. The method according to claim 1,characterized inthat said extruded housing (10) at least along itslongitudinal parallel enclosing edges is provided with an undercut slot(14a, 14b) for the reception of a stiffening plastics or metal platemember.
 3. The method according to claim 1, characterized inthat thelongitudinal parallel enclosing edges (12a, 12b) of said extrudedhousing (10) are provided with an internal slot forming a thinattachment slot (13a, 13b) for a label having article information andbeing inserted under a portion of the outer enclosing parts directedtowards the center of the price-marking device.
 4. The method accordingto claim 1, characterized inthat the biasing force of the longitudinalparallel enclosing edges (12a, 12b) is accomplished by means of thelongitudinal parallel enclosing edges (12a, 12b) upon extrudation areobtaining a slightly inward inclined direction towards the rear side ofsaid housing (10).
 5. The method according to claim 1, characterizedinthat the front glass (33) of said thin LCD on which the terminalfields for electric connection of said thin LCD are present, is madeslightly wider that the rear glass (32), whereby an alignment andsupport edge for said zebra contact strip (15) is obtained along theupper and/or lower edge of said rear glass (32).
 6. An arrangement forprice-marking device (1) comprising a thin LCD (30) and a printedcircuit board (20) with control electronics and power supply, e.g. asolar cell, said thin LCD (30) being connected to said printed circuitboard (20) by means of a connection device of conductive rubber in formof a so called zebra contact strip (15), characterized inthat said zebracontact strip (15) in a longitudinal direction of the conducting rubberareas is arranged compressed between said thin LCD (30) and said printedcircuit board (20) by means of longitudinal parallel enclosing edges(12a, 12b) of the extruded housing (10), preferably made of plasticmaterial, and which longitudinal parallel enclosing edges (12a, 12b)upon production through extrudation are provided with an inward directedbiasing force, that at least the longitudinal parallel enclosing edges(12a, 12b) of said housing in design and material are arranged biasedsuch that inner surfaces of said longitudinal parallel enclosing edgescentered over the center of the zebra contact (15) along thecorresponding edges of said thin LCD (30) and said printed circuit board(20) comprising terminal fields (21, 22) for signal transmission betweensaid thin LCD and the printed circuit board are acting as a leverexerting pressure against a glass (33) constituting the front side ofsaid thin LCD, whereby these longitudinal parallel enclosing edgessupply a compression of at least 15% of the conducting rubber of saidzebra contact (15).
 7. The arrangement according to claim 6,characterized inthat said extruded housing (10) at least along itslongitudinal parallel enclosing edges is provided with an undercut slot(14a, 14b) for reception of a stiffening plastics or metal plate member.8. The arrangement according to claim 7, characterized inthat thelongitudinal parallel enclosing edges (12a, 12b) of said extrudedhousing (10) are provided with an internal slot creating a thinattachment slot (13a, 13b) for a label provided with article informationand being inserted under a portion of the outer enclosing parts whichare directed towards the center of the price-marking device.
 9. Thearrangement according to claim 8, characterized in that the longitudinalparallel enclosing edges (12a, 12b) upon extrudation are slightlydirected inward inclined towards the rear side of said housing (10). 10.The arrangement according to claim 6, characterized inthat the frontglass (33) of said thin LCD on which terminal fields for electricconnection of said thin LCD are present, is made slightly wider than therear glass (32), whereby an alignment and support edge for said zebracontact strip (15) is obtained along the upper and/or lower edge of saidrear glass (32).
 11. The method according to claim 2, characterizedinthat the front glass (33) of said thin LCD on which the terminalfields for electric connection of said thin LCD are present, is madeslightly wider than the rear glass (32), whereby an alignment andsupport edge for said zebra contact strip (15) is obtained along theupper and/or lower edge of said rear glass (32).
 12. The methodaccording to claim 3, characterized inthat the front glass (33) of saidthin LCD on which the terminal fields for electric connection of saidthin LCD are present, is made slightly wider than the rear glass (32),whereby an alignment and support edge for said zebra contact strip (15)is obtained along the upper and/or lower edge of said rear glass (32).13. The method according to claim 4, characterized inthat the frontglass (33) of said thin LCD on which the terminal fields for electricconnection of said thin LCD are present, is made slightly wider than therear glass (32), whereby an alignment and support edge for said zebracontact strip (15) is obtained along the upper and/or lower edge of saidrear glass (32).
 14. The arrangement according to claim 7, characterizedinthat the front glass (33) of said thin LCD on which terminal fieldsfor electric connection of said thin LCD are present, is made slightlywider than the rear glass (32), whereby an alignment and support edgefor said zebra contact strip (15) is obtained along the upper and/orlower edge of said rear glass (32).
 15. The arrangement according toclaim 8, characterized inthat the front glass (33) of said thin LCD onwhich terminal fields for electric connection of said thin LCD arepresent, is made slightly wider than the rear glass (32), whereby analignment and support edge for said zebra contact strip (15) is obtainedalong the upper and/or lower edge of said rear glass (32).
 16. Thearrangement according to claim 9, characterized inthat the front glass(33) of said thin LCD on which terminal fields for electric connectionof said thin LCD are present, is made slightly wider than the rear glass(32), whereby an alignment and support edge for said zebra contact strip(15) is obtained along the upper and/or lower edge of said rear glass(32).
 17. A price marking device, comprising:a liquid crystal displaycomprising connector terminals; a printed circuit board comprisingterminal fields; a zebra contact strip, positioned between and incontact with said liquid crystal display and said printed circuit, andcomprising conductive rubber areas, said conductive rubber areaselectrically connecting said connector terminals to said terminalfields; and means for confining together said liquid crystal display,said printed circuit board and said zebra contact strip and forcompressing said conductive rubber areas, in a longitudinal directionextending between said liquid crystal display and said printed circuitboard, by at least about 15%.
 18. The price marking device of claim 17wherein said confining and compressing means comprises a housing havinga rear side adjacent said printed circuit board and longitudinalparallel enclosing edges coupled to said rear side and being adjacentsaid liquid crystal display, said longitudinal parallel enclosing edgesbeing configured to urge said liquid crystal display towards said rearsurface to compress said conductive rubber areas said at least about15%.
 19. The price marking device of claim 18 wherein said longitudinalparallel enclosing edges are biased towards said rear wall.
 20. Theprice marking device of claim 18 wherein said longitudinal parallelenclosing edges comprises first longitudinal parallel enclosing edgesand second longitudinal parallel enclosing edges.
 21. The price markingdevice of claim 20 wherein said printed circuit board has a first edgeadjacent first terminal fields and a second edge adjacent secondterminal fields, said liquid crystal display has one edge adjacent firstconnector terminals and another edge adjacent second connectorterminals, and said zebra contact strip has a first edge segmentadjacent first conductive rubber areas and a second edge segmentadjacent second conductive rubber areas, and further wherein said firstlongitudinal parallel enclosing edges comprise a first enclosing edgeportion and said second longitudinal parallel enclosing edges comprise asecond enclosing edge portion, said first enclosing edge portion beingcentered over said first conductive rubber areas and being configured tourge said one edge towards said rear surface to compress said firstconductive rubber areas said at least about 15%, and said secondenclosing edge portion being centered over said second conductive rubberareas and being configured to urge said another edge towards said rearsurface to compress said second conductive rubber areas said at leastabout 15%.